1. Field of the Invention
This invention relates to steering arrangements provided on solid axles, including steerable four-wheel drive solid axles, and more particularly pertains to a method and apparatus for adjusting caster and camber geometry at such yoke and steering knuckle arrangement.
2. Description of the Prior Art
Vehicles, such as trucks, four-wheel and front-wheel drive conveyances often employ a solid steerable front axle arrangement in which a yoke is fixedly attached to the solid axle. Pivoting means, such as ball joints, are interposed between the yoke and a steering knuckle which in turn carries a spindle upon which the wheel is mounted for rotation. When forces are introduced through, for instance, a steering arm, the steering knuckle pivots relative to the yoke and axle to provide steering at the attached wheels.
Caster and camber adjustments, particularly camber adjustments, are quite critical to proper road handling and tire wear. Particularly when wide, high floatation tires--such as are common on four-wheel drive vehicles--are employed, misadjustments of camber may cause only a limited portion of the bottom of the tire to contact the supporting surface. This results not only in greatly accelerated tire wear, but compromises safe handling on rigid highway surfaces, and may lead to overheating of the small contact patch of the tire at higher speeds. Heretofore only limited means have been available to adjust camber and essentially no means exist for accomplishing caster adjustments which influence straight line tracking and turning camber of the vehicle. Classically, the drawbacks of improper caster and camber adjustment have been accepted with high costs in tire wear and comprised road handling and safety. In some instances, particularly in non-four-wheel drive vehicles, camber has been adjusted by bending the solid axle to position the tire in a more or less desired camber arrangement. However, such bending has not been widely accepted in the case of four-wheel drive vehicles which employ a tubular axle housing. Space is not available to position a bending device on such tubular axle, and the hollow axle housing is subject to stress failure.
Another approach to adjusting camber is discussed in U.S. Letters Pat. No. 4,037,680 issued July 26, 1977, to Clinton E. Grove. According to such prior patent a tapered shim is introduced between the spindle mounting means and the spindle to provide for adjustment of the angular position of the spindle relative to the solid axle and yoke. However, to accomplish such adjustment, the hub, spindle and other associated wheel mounting means must be first removed. Accordingly, a great deal of work is involved in positioning such shims. Since the shim does not change the steering geometry, no change in caster alignment is possible with such a system. Accordingly, such shims, though operable and a worthwhile improvement over the entire absence of a workable camber adjustment, are inconvenient and time consuming, and accordingly quite expensive to employ. Also, such shims do not provide for caster adjustment.